Histo - Muscle Tissue Flashcards
1
Q
Muscle tissue develops from ____
A
mesoderm
2
Q
The cytoplasm in muscle cells is called ___
A
sacroplasm
3
Q
What is the sarcoplasm?
A
the cytoplasm of muscle cells
4
Q
The smooth endoplasmic reticulum in muscle cells is called _____
A
sarcoplasmic reticulum
*has new/important role in muscle cells
5
Q
What is the sarcoplasmic reticulum?
A
the smooth endoplasmic reticulum in muscle cells
*has new/important role in muscle cells
6
Q
The plasma membrane / plasmalemma of muscle cells is called _____
A
sarcolemma
7
Q
What is the sarcolemma?
A
The plasma membrane / plasmelemma of muscle cells
8
Q
What is a muscle cell called?
A
muscle fiber or myofiber
9
Q
Describe the difference between a muscle fiber and a nervous fiber
A
Nervous fiber is just an axon
Muscle fiber is the entire cell
10
Q
What are the 3 muscle prefixes
A
sarco-, myo-, mys-
11
Q
Do muscle organs contain only muscle tissue?
A
no.
by definition, an organ contains two or more primary tissue types, so it must contain other tissue besides muscle tissue
12
Q
What are the 3 types of muscle tissue based on functional traits?
A
1 skeletal muscle tissue
2 cardiac muscle tissue
3 smooth muscle tissue
13
Q
Describe the contraction of a skeletal muscle tissue
A
strong, quick, discontinuous, voluntary contraction
14
Q
Describe the contraction of a cardiac muscle tissue
A
strong, quick, continuous, involuntary contraction
15
Q
Describe the contraction of a smooth muscle tissue
A
weak, slow, involuntary contraction
16
Q
What are 4 special characteristics of muscle tissue?
A
1 excitability/irritability
2 contractability
3 extensibility
4 elasticity
17
Q
Special characteristic of muscle tissue: excitability/irritability.
Describe this.
A
ability to respond to a stimulus via electrical signal (like a neuronal axon)
can produce/conduct action potentials
18
Q
Special characteristic of muscle tissue: contractability.
Describe this.
A
When tension by a muscle is greater than resistance to a force, the muscle shortens
whether or not muscle shortens, contraction is occurring
19
Q
Special characteristic of muscle tissue: extensibility.
Describe this.
A
muscle tissue is able to be extended and stressed
*this is a passive process
20
Q
Special characteristic of muscle tissue: elasticity.
Describe this.
A
muscle tissue’s ability to return to original length after being shortened or lengthened.
21
Q
What are the 4 functions of muscle tissue?
A
1 produce movement
2 maintain posture
3 stabilize joints
4 generate heat
22
Q
Describe how muscle tissue produces movement (function)
A
skeletal muscle tissue - moves things from 1 location to another
smooth muscle tissue - moves things within urinary/gi tract through peristalsis
cardiac muscle tissue - move blood throughout cardiac system
23
Q
Describe how muscle tissue maintains posture (function)
A
*mostly skeletal muscle
muscles are constantly fighting gravity so muscles must contract to maintain posture
24
Q
Describe why sitting with your back unsupported leads to back pain
A
Skeletal muscles play a large role in maintaining posture
If back is unsupported, muscles maintaining posture must do more work, this leads to back pain
25
Describe why muscle tissue stabilizes joints (function)
*mostly skeletal
because muscles and joints = movement
and muscle tissue plays large role in movement
26
Describe why muscle tissues generate heat (function)
thermogenesis
muscle cells and tissues are generating ATP to generate a force. this is exothermic
think: shivering at bus stop.
27
Skeletal muscle: striated/nonstriated? Why?
striated.
because of arrangement of actin and myosin
28
Describe the cell shape of skeletal muscle cells
```
large, elongated, cylindrical cells
structural syncitiated (multinucleated) cells
```
elongated because muscle cells run the entire length of the muscle
29
How long are skeletal muscles?
skeletal muscle cells are elongated.
they run the length of the muscle
30
Describe nucleus placement of skeletal muscle cells
nuclei are at the periphery just beneath the sarcolemma
31
Describe why skeletal muscle cells are a structural syncytium
skeletal cells are a fusion of embryonic myoblasts, leading to them being multinucleated
this means that skeletal muscle cells are a STRUCTURAL syncitium
32
Skeletal muscle cells are a fusion of embryonic _____. This means that they are what?
myoblasts
this means that they are multinucleated aka structural syncitium.
33
Cardiac muscle cells are a strong, quick contraction followed by _____
quick relaxation period
34
Describe the cell shape of cardiac muscle cells
elongated, branched cells joined by intercalated discs
35
Are cardiac muscle cells multinucleated or uninucleated?
uninucleated
occasionally you will see a slide with 2 nuclei in 1 cell, this is rare.
36
What are intercalated discs? Which muscle cell type are they in?
cardiac muscle
they are eosinophilic lines that connect cardiac muscle cells to each other to keep cells together physically
gap junctions in intercalated discs allow cells to become a FUNCTIONAL syncitium.
this allows cardiac muscle cells to be "interwoven"
37
Which muscle cell type is a structural syncitium? which is a functional syncitium?
structural syncitium = skeletal muscle cells due to embryonic fusion of myoblasts
functional syncitium = cardiac muscle cells due to intercalated disc's gap junctions connecting them to each other
38
Are cardiac muscle cells striated or nonstriated?
striated (seen in longitudinal cross section)
but striation is broken apart by cardiac muscle cell's branching. so it appears different than skeletal striation
39
Compare/contrast the striation patterns of skeletal and cardiac muscle cells
Skeletal muscle cells = uninterrupted striated pattern
Cardiac muscle cells = interrupted striated pattern due to branching (mostly) and intercalated discs
40
Where is the nucleus located in cardiac muscle cells?
Nucleus is centered inside the cardiac muscle cell
41
Are smooth muscle cells striated or non striated?
Non striated
Their actin and myosin are arranged in a completely different orientation than skeletal/cardiac muscle cells
42
Are smooth muscle cells uninucleated or multinucleated?
uninucleated.
43
Describe the cell shape of smooth muscle cells
fusiform (wide centered, tapered on edges)
nucleus is located in the widest part of the fusiform cell
44
Where are smooth muscle cells found?
in walls of hollow organs needed to proper things forward
gi, urinary, reproductive, respiratory, iris of eye, blood vessels
45
What is the average length of a smooth muscle cell?
HIGHLY variable
think: can be in blood vessel or in pregnant uterus
46
How are smooth muscle cells usually oriented with each other?
smooth muscle is usually laid down in "sheets" in same direction with alternating pattern
this is helpful for propelling substances forward throughout a tract
47
What are the 3 classifications of skeletal muscle in humans?
What are they classified based on?
classified based on physiology, biochemistry, histochemistry
type 1: slow, red oxidative fibers
type 2a: fast, intermediate oxidative-glytolytic fibers
type 2b: fast, white glycolytic fibers
48
Type 1: slow, red oxidative fibers (skeletal muscle)
describe the amount of myoglobin, mitochondria and glycogen.
many mitochondria and myoglobin present (this is why it is red in color)
49
What is myoglobin?
oxygen-binding protein
50
Type 1: slow, red oxidative fibers (skeletal muscle)
Why is it red?
because so much oxygen due to the high levels of myoglobin (oxygen binding protein) and mitochondria
51
Type 1: slow, red oxidative fibers (skeletal muscle)
derives energy primarily from ____
aerobic oxidative phosphorylation of fatty acids
52
Type 1: slow, red oxidative fibers (skeletal muscle)
Describe the diameter relative to the other types of fibers
relatively small diameter relative to type IIa and type IIb of skeletal muscles
small = least powerful
53
Type 1: slow, red oxidative fibers (skeletal muscle)
Adapted for what type of contractions? What's an example of this?
slow, continuous contractions over long periods of time
| example: muscles to maintain posture
54
Type 2a: fast, intermediate oxidative-glycolytic fibers (skeletal muscle)
describe the amount of myoglobin, mitochondria and glycogen.
many mitochondria, lots of myoglobin AND glycogen (because it is intermediate)
55
Type 2a: fast, intermediate oxidative-glycolytic fibers (skeletal muscle)
Describe the diameter relative to the other 2 fibers
Diameter size is intermediate between type I and type IIb skeletal muscle fibers
56
Type 2a: fast, intermediate oxidative-glycolytic fibers (skeletal muscle)
derives energy primarily from ___
oxidative metabolism and anaerobic glycolysis
| intermediate
57
Type 2a: fast, intermediate oxidative-glycolytic fibers (skeletal muscle)
Adapted for what type of contractions?
Rapid contractions and short bursts of activity
58
Type 2b: fast, white glycolytic fibers (skeletal muscle)
describe the amount of myoglobin, mitochondria and glycogen.
Fewer mitochondria and myoglobin
LOTS of glycogen (which makes it pale or white looking)
59
Type 2b: fast, white glycolytic fibers (skeletal muscle)
Why is it white?
because of the glycogen present
60
Type 2b: fast, white glycolytic fibers (skeletal muscle)
Energy is derived primarily from _____
anaerobic glycolysis
61
Type 2b: fast, white glycolytic fibers (skeletal muscle)
Adapted for what type of contraction/ What is an example of this?
Rapid contractions (that fatigue easily)
Example: weight lifting, throwing baseballs, etc.
62
Most muscles contain which type of muscle fiber?
most muscles are a combination of muscle fiber types
may have more of one type depending on it's function and/or genetics
63
Myofibrils take up ___% of cytoplasm?
80
64
Describe myofibrils physically
long, cylindrical rods runnung parallel to long axis of the cell
~2um in diameter
65
The myofibril pattern is made up because of what?
sarcomere
66
What is the smallest unit of contraction?
sarcomere
67
A sarcomere is made up of?
It extends from what to what?
extends from z disc to z disc
is 1/2 i band, entire a band, 1/2 i band
68
How do sarcomeres line up to create a striated pattern?
sarcomeres of 1 myofibril line up laterally with those on the next and the next and the next...
69
What is the area called where you see thick filament?
a band
70
Thick filament aka ____
myosin filament
71
What is the area called where you see thin filament only?
i band
72
Thin filament aka ____
actin filament
73
Which is dark/light on a histo slide?
A band is dArk
I band is lIght
74
Describe what is found in both a band and i band
a band is where any thick filament (myosin) is found
i band is where thin filament (actin) ONLY is found
75
What is the area of thick filament only called?
H zone
NO THIN FILAMENT (ACTIN) HERE
76
Where is the h zone? What is found there?
the h zone is the center of the a band / center of the sarcomere
this is where thick filament (myosin) only is found.
no thin filament (actin) is found here
77
What is the center of the h zone?
the m line
78
What is the m line?
| What is found there?
the center of the h zone
contains proteins that connect myosin together to maintain the structure of sarcomeres
79
What is the normal length of a sarcomere?
~2.5um
| the distance changes when it contracts/relaxes
80
When is the h zone present?
in a relaxed muscle
(think: if contracted, myosin bind to actin and pulls it inward. therefore there is no area with "thick filament only" since the thin filament is overlying the thick. therefore the h zone disappears)
81
What is the sliding filament hypothesis?
the theory that myosin pulls actin towards center of the sarcomere as a means of contraction
82
Does contraction = shortening
no.
| but if the force is greater than the resistance, then shortening will occur
83
As myosin pulls actin towards the center, what happens to the h zone?
h zone gets smaller and ultimately disappears
84
As myosin pulls actin towards the center, what happens to the i band?
the i band gets smaller and ultimately disappears
85
As myosin pulls actin towards the center, what happens to the a band?
the a band remains the same length
86
As myosin pulls actin towards the center, what happens to the z discs?
z discs are pulled together in this processes.
this means that the sarcomere shrinks, the myofibril shrinks and the cell overall gets shorter
87
As myosin pulls actin towards the center, what happens to the length of myosin/actin?
they remain the same length
the way that they are overlapping is what changes.
88
Thick filament (myosin) is made up of ____
2 heavy interwoven polypeptide chains
has 2 globular heads at either end
89
What is located at the globular head ends of myosin?
actin binding sites, atp binding sites and atpase activity
90
How many myosin molecules compose 1 thick myofilament?
several hundred
91
Thin filament (actin) is made up of ____
globular subunits (g actin)
2 strands of g actin twisting together, each has a myosin binding site that is blocked by tropomyosin
92
What is g actin?
the globular subunit of actin
2 g actins twisting together = actin
93
The myosin binding site on g actin is blocked by ____
tropomyosin
94
What is tropomyosin?
long, thin molecules twist around actin filaments
blocks myosin binding site n g actin (globular subunit of actin)
95
What is troponin and it's subunits?
TNT: attaches troponin to tropomyosin
TNC: binds calcium ions (important because calcium is the final signal for contraction)
TNI: inhibitor of actin/myosin interaction
96
What is the TNT subunit of troponin responsible for?
attaching troponin to tropomyosin
97
What is the TNC subunit of troponin responsible for?
binding calcium
calcium is the final stage for muscle contraction
98
What is the TNI subunit of troponin responsible for?
inhibiting actin/myosin interactions
99
What are t tubules?
extensions of the sarcolema (plasma membrane)
100
Extensions of the sarcolema are called ___
t tubules
101
What is the enlarged part of the sarcoplasmic reticulum called? Why is it enlarged?
terminal cisterna
it is storing calcium ions
102
What is the part of the sarcoplasmic reticulum called that stores calcium ions?
terminal cisterna
this is the enlarged part of the sarcoplasmic reticulum
103
What is a skeletal muscle triad made up of?
1 t tubule
| 2 terminal cisterna
104
1 t tubule and 2 terminal cisterna come together to make up a ____
Where is this found?
skeletal muscle triad
this is present 2x in a sarcomere (at each i band/a band junction)
105
What is found at the I band A band junction?
a skeletal muscle triad
this is found twice per sarcomere (because there are 2 a band/i band junctions in a sarcomere)
106
What connects the t tubules and the terminal cisterna?
voltage-gated regulatory proteins
107
When an action potential comes down from the t tubules towards the terminal cisterna, it first hits the ____
voltage-gated regulatory proteins
108
What happens with the action potential hits the voltage-gated regulatory proteins in between the t tubules and the terminal cisterna?
these regulatory proteins undergo a conformational change which causes the release of Ca from the terminal cisterna
109
Ca from the terminal cisterna is due to what?
conformational change of voltage-gated regulatory proteins causes the release of Ca from termianl cisterna
110
Once Ca is released from terminal cisterna, what is the intracellular calcium level?
high
this is the final stage of contraction
111
Neuromuscular junction aka ____
motor end plate
112
What is the neuromuscular junction?
aka motor end plate
chemical synapse between motor (efferent) neurons and skeletal muscle fibers/cells
113
What is a motor unit?
a motor (efferent) neuron and all of the muscle fibers (cells) that it interacts with
114
What happens to muscle fibers if the motor unit is activated?
How many muscle fibers per motor unit?
ALL of the skeletal muscle cells contract (can have 1 - 160 muscle fibers per motor unit)
115
How are motor units different in areas of fine motor control?
In areas of fine motor control = small motor unit
compared to lower limb = lots of big motor units
116
An action potential comes down a motor neuron and hits the ____
neuromuscular junction
117
How does the axon terminal of motor neuron and the plasma membrane of skeletal muscle cell interact during action potential contraction flow?
axon terminal of motor neuron gets close (does not touch) skeletal muscle cell plasma membrane
118
Action potential of motor neuron releases calcium, causing ___
releases calcium via voltage gated channels
this causes calcium to flood into the axon terminals
causes release of ACh
Causes graded potential of sarcolemma
119
Voltaged gated channels on the plasma membrane of skeleta musclecell create another AP, which travels through ___
T Tubules
120
T tubules interact with terminal cisterna at the ____
How does the terminal cisterna release Calcium?
triad
conformational change of the terminal cisternae causes releases of calcium
121
What kind of energy state is myosin in?
high energy state
myosin is in high energy state waiting for actin to build a cross bridge
122
Do globular heads of myosin pull all at once?
no.
if they pulled all at once, they would "snap back" to original orientation. They pull in waves
123
As myosin goes from high energy to low energy, ____ is released
ADP and phosphate
124
How does the cross bridge break between myosin and actin?
ATP binds to globular head
125
Describe rigor mortis (and timeline) in terms of calcium and ATP
When dead, calcium floods into cell, binds to troponin, moves tropomyosin, myosin/actin cross bridge form.
Because dead, no ATP formation. So cross bridge cannot break.
This starts 3-4 hours after death, peaks at 12 hours, and dissipates 48-60 hours because of prolyolytic enzymes from lysosomes which degrade cells
126
Skeletal muscle (the organ) contains what 4 components?
1. skeleta muscle tissue
2. vessels (arteries, capillaries, veins, lymph nodes)
3. Nerve fibers
4. Connective tissue
127
What are the 3 connective tissue sheaths associated with skeletal muscle (the organ)?
endomysium
perimysium
epimysium
128
Are the three connective tissue sheaths associated with skeletal muscle (the organ) completely separate or connected?
endomysium, perimysium and epimysium are all connected
129
Describe endomysium
delicate layer of connective tissue surrounding individual skeletal muscle fibers
130
Describe perimysium
many skeletal muscle fibers together are wrapped in perimysium.
perimysium wrapped structures are known as fassicles
131
What is a fassicle?
Perimysium wrapped structures are known as fassicles
132
Describe epimysium
All fassicles together are wrapped in epimysium
External sheath, dense connective tissue surrounding entire muscle
133
If you were handed a muscle - what connective tissue sheath would you be touching?
epimysium
134
Walk through the contraction stages from myofibril contraction to bone.
myofibril -> cell -> endomysium -> perimysium -> epimysium -> tendon -> bone
135
The tendon connects what to what?
connects epimysium of muscle to periosteum of bone
136
What do sharpey's fibers connect?
periosteum of bone to bone tissue
137
What connects the periosteum of bone to the bone tissue?
sharpey's fibers
138
Compare cardiac m and skeletal m:
Striation?
Skeletal m: striated
Cardiac m: striated, but less so because of branching
139
Compare cardiac m and skeletal m:
cell shape/nucleus
Skeletal: long, cyllindrical, multinucleated, nuclei located under sarcolemma
Cardiac: short, fat, branched, 1 nucleus in center
140
Compare cardiac m and skeletal m:
contraction
both operate under sliding filament mechanism.
141
Compare cardiac m and skeletal m:
Mitochondria in cell volume
Skeletal m: mitochondria are 2% cell volume
Cardiac m: large mitochondria are 25-40% of cell volume
142
Compare cardiac m and skeletal m:
Sarcomeres
both have z discs, a band, i band
143
Compare cardiac m and skeletal m:
T tubules. How many and where are they?
Skeletal m: 2 t tubules per sarcomere @ a-i junction
Cardiac m: 1 t tubule per sarcomere @ z line
144
Compare cardiac m and skeletal m:
diad/triad
sarcoplasmic reticulum complex or simple? big/small terminal cisterna?
Skeletal m: triad
- complex sarcoplasmic reticulum with large terminal cisterna and 2 t tubules
cardiac m: diad
- simple sarcoplasmic reticulum with small terminal cisterna and 1 t tubule
145
What are the 2 jobs of intercalated discs in cardiac muscle cells?
1. make sure cells dont let go of each other
| 2. make sure cells communicate and work as 1 (functional syncitium)
146
How do intercalated discs of cardiac muscle cells stain histologically?
dark lines that traverse the slide
147
What are the 3 components of intercalated discs of cardiac muscle cells?
1. fascia adherens
2. desmosomes (macula adherens)
3. gap junction
148
Fascia adherens of intercalated discs in cardiac muscle cells
Describe what they do/what they connect
Connect actin of 1 cell to actin of another cell (they function like z discs)
they form an anchoring junction
149
Desmosomes of intercalated discs in cardiac muscle cells
Describe what they do/what they connect
Desmosomes aka ____
desmosomes aka macula adherens
connect intermediate filaments of 1 cell to intermediate filaments of another cell
they form an anchoring junction
150
Gap junctions of intercalated discs in cardiac muscle cells
What do they do?
These serve for intracellular communication
They form a communication junction
So if 1 cell gets the signal to contract, they all get the signal to contract. This is how cardiac muscles function as functional syncitium
151
How are cardiac muscle cells able to function as a functional syncitium?
gap junctions of intercalated discs of cardiac muscle cells serve as intracellular communication junctions.
this is how they operate as a functional syncitium
152
What connective tissue sheath is present in the smooth muscle cells
endomysium
153
What produces endomysium in smooth muscle cells?
Why is this different than normal?
endomysium is produced by smooth muscle cells
usually, fibroblasts produce connective tissue, this is different here.
154
Do smooth muscle cells have a sarcoplasmic reticulum?
Yes. It is rudimentary.
It is present for calcium contraction
155
Do smooth muscle cells have t tubules?
No t tubules because actin and myosin line up differently here
156
How do actin and mysoin line up in smooth muscle cells?
in a lattice network
they cross obliquely across the cell, this is why smooth muscle isn't striated
157
Describe the contraction of a smooth muscle cell
Corkscrew twist, brings nucleus down with it.
Still contracts based on the sliding filament mechanism
158
Actin filaments of smooth muscle are tied into ____ (which are located ___)
dense bodies
these are located inside the cell at the surface
